Numerous studies have unequivocally demonstrated the real possibility for a prenatal carcinogenic insult resulting in the immediate offspring developing cancer. The objective for this proposal is to establish whether a perinatal iodine-131 shock will increase the risk of cancer occurring in both the first generation offspring and their subsequent progeny. This project has been designed to test the hypothesis that upon exposure to iodine-131 during pregnancy there occurs information incorporation of the carcinogenic insult in both the somatic and germ cells; and, this message can then be recalled at a later stage in both the immediate, as well as future offspring, a type of geneological memory occurrence, which is exhibited in the overt form of cancer. The experimental testing of this hypothesis will be accomplished by determining the specific antitumor cell-mediated immunity (CMI) induced in Fischer F344 inbred rats, such responses will be measured in both the dams and three generations of offspring at 2 months postpartum following exposures to the mothers consisting of 0.1 to 100 MuCi (0.37-3.7 MBq) of Na131I during days 4, 8, 12, and 16 of pregnancy. The geneological memory will then be established by determining the Radiation Recall for the exposure following a subsequent insult to the colon carcinogen 1,2-dimethylhydrazine. We have already completed the initial phase of the proposed studies and have established the existence of antitumor immunity in the first generation offspring born from mothers exposed to the radioiodine on day 16 of gestation. It was observed that there may exist a hormonal component involved in the radioiodine effects since the male pups were nearly 1.7 times more responsive than their sisters with the threshold detection level being found to be in the range of 250 nCi (9.25 kBq). Certainly with the increasing utilization of nuclear technology, it is of upmost importance that our society have an understanding about the possible related health hazards; consequently, the present project has been designed to apply an analytical technique which we have previously developed in order to gather information about the possible increases in cancer rates which might be related with accidental radioiodine exposures.